Abstract: An actuator drive circuit includes a counter starting counting of a frequency-divided clock obtained by dividing a frequency of a reference clock in response to an activation signal, a D/A converter providing a converted voltage increasing gradually and stepwise in response to an output of the counter, a coil current control amplifier comparing a coil current detection voltage corresponding to a value of a coil current of the actuator with the converted voltage immediately after activation, comparing the coil current detection voltage with a coil current limitation reference voltage corresponding to an upper limit value of the coil current after the converted voltage matches the coil current limitation reference voltage, and providing an amplified output voltage prepared by amplifying a difference between the compared voltages, and a drive current output circuit providing a drive current of the actuator according to the amplified output voltage of the coil current control amplifier.

Abstract: A stable high-precision current detection circuit capable of continuously detecting load current through a load with extremely reduced power loss. The current detection circuit has a power transistor and a current detection transistor that are fed with a common power supply voltage and a common switching signal. A buffer circuit is provided for supplying an idling current to the output node of the current detection transistor while realizing the same virtual potential at the output terminals of these transistors. Thus, the buffer circuit always functions as a class-A amplifier.

Abstract: A stable high-precision current detection circuit capable of continuously detecting load current through a load with extremely reduced power loss. The current detection circuit has a power transistor and a current detection transistor that are fed with a common power supply voltage and a common switching signal. A buffer circuit is provided for supplying an idling current to the output node of the current detection transistor while realizing the same virtual potential at the output terminals of these transistors. Thus, the buffer circuit always functions as a class-A amplifier.

Abstract: A shutter actuator drive circuit capable of operating an actuator with precision is provided.